Vendor Risk Management for SaaS: How to Assess and Monitor Third-Party Risk

Third-party risk management for SaaS has never been more important. High-profile supply chain attacks and vendor data breaches have demonstrated that your security posture is only as strong as your weakest vendor. A formal vendor risk programme doesn't need to be complex — but it does need to be consistent.

Tier Your Vendors by Risk

Not every vendor deserves the same scrutiny. A tool that processes your customer data under a data processing agreement is a critical vendor. A tool used by three employees for internal documentation is low risk. Define three risk tiers based on data sensitivity, user count, and integration depth, and apply proportionate review to each.

What to Assess

For critical vendors: SOC 2 Type II report (verify it's current and covers the services you use), penetration testing evidence, data residency confirmation, sub-processor list, breach notification process and history, and financial stability. For mid-tier vendors: SOC 2 or equivalent, data residency, sub-processor list. For low-risk vendors: privacy policy review and DPA signature.

Ongoing Monitoring

Initial vendor assessment is a point-in-time snapshot. Ongoing monitoring catches changes that increase risk: vendor acquisitions, significant personnel changes in their security team, published CVEs affecting their infrastructure, and breach disclosures. Subscribe to your critical vendors' security advisories and set up news alerts.

Contractual Risk Controls

Vendor risk management is not only an assessment exercise — it requires contractual controls that define the vendor's obligations and your remedies if they fail to meet them. Key contractual provisions for critical vendors include: a right to audit (or a requirement to provide annual SOC 2 reports), notification obligations for security incidents and material sub-processor changes, data deletion requirements on contract termination, uptime and SLA commitments with defined remedies for failure, and termination rights in the event of a material security failure.

Standardise your contractual requirements by vendor tier and include them in your RFP and negotiation process as non-negotiable baseline terms for critical vendors. Vendors who refuse standard contractual security requirements are a risk signal in themselves — a vendor confident in their security posture doesn't typically resist reasonable audit and notification obligations.

Building a Vendor Risk Register

Maintain a vendor risk register that records, for each critical and mid-tier vendor: the date of last security assessment, the assessment outcome (rating and any open findings), the date the vendor's SOC 2 or equivalent was last reviewed, any open risk items and their status, and the next scheduled review date. This register is the evidence your auditors want to see for third-party risk management, and it ensures that vendor reviews actually happen on schedule rather than being crowded out by day-to-day operational demands.

Link the vendor risk register to your software inventory so that each tool record shows its vendor's risk rating and last assessment date. This gives IT and Finance instant visibility into which tools carry elevated vendor risk — useful context when making renewal decisions, particularly if a vendor's risk profile has deteriorated since the initial procurement assessment.

Concentration Risk: When One Vendor Holds Too Much

Beyond individual vendor risk, consider concentration risk: the risk that too many critical workflows depend on a single vendor or a small group of vendors. An organisation where Microsoft provides email, document management, identity, communication, and endpoint management has significant concentration risk — a major Microsoft outage or a compromise of their services would be broadly disruptive. Identify your highest-concentration vendors and assess whether the risk is accepted (and mitigated with appropriate incident response planning) or whether diversification is warranted for specific critical functions.